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        .box {
            margin: 100px auto;
            width: 642px;
            height: 432px;
            background-color: #000;
            overflow: hidden;
        }
        ul {
            margin: 1px;
            width: 630px;
            height: 420px;
            border-top: 10px solid #000;
            border-left: 10px solid #000;
            overflow: hidden;
        }
        li {
            list-style: none;
            border-right: 10px solid #000;
            border-bottom: 10px solid #000; 
            width: 200px;
            height: 200px;
            float: left;
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        li a {
            display: block;
            width: 100%;
            height: 100%;
            background-color: white;
        }

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